33,633 research outputs found
Design and Reliability Performance Evaluation of Network Coding Schemes for Lossy Wireless Networks
This thesis investigates lossy wireless networks, which are wireless communication networks consisting of lossy wireless links, where the packet transmission via a lossy wireless link is successful with a certain value of probability. In particular, this thesis analyses all-to-all broadcast in lossy wireless networks, where every node has a native packet to transmit to all other nodes in the network. A challenge of all-to-all broadcast in lossy wireless networks is the reliability, which is defined as the probability that every node in the network successfully obtains a copy of the native packets of all other nodes. In this thesis, two novel network coding schemes are proposed, which are the neighbour network coding scheme and the random neighbour network coding scheme. In the two proposed network coding schemes, a node may perform a bit-wise exclusive or (XOR) operation to combine the native packet of itself and the native packet of its neighbour, called the coding neighbour, into an XOR coded packet. The reliability of all-to-all broadcast under both the proposed network coding schemes is investigated analytically using Markov chains. It is shown that the reliability of all-to-all broadcast can be improved considerably by employing the proposed network coding schemes, compared with non-coded networks with the same link conditions, i.e. same probabilities of successful packet transmission via wireless channels. Further, the proposed schemes take the link conditions of each node into account to maximise the reliability of a given network. To be more precise, the first scheme proposes the optimal coding neighbour selection method while the second scheme introduces a tuning parameter to control the probability that a node performs network coding at each transmission. The observation that channel condition can have a significant impact on the performance of network coding schemes is expected to be applicable to other network coding schemes for lossy wireless networks
Design and Reliability Performance Evaluation of Network Coding Schemes for Lossy Wireless Networks
This thesis investigates lossy wireless networks, which are wireless communication networks consisting of lossy wireless links, where the packet transmission via a lossy wireless link is successful with a certain value of probability. In particular, this thesis analyses all-to-all broadcast in lossy wireless networks, where every node has a native packet to transmit to all other nodes in the network. A challenge of all-to-all broadcast in lossy wireless networks is the reliability, which is defined as the probability that every node in the network successfully obtains a copy of the native packets of all other nodes. In this thesis, two novel network coding schemes are proposed, which are the neighbour network coding scheme and the random neighbour network coding scheme. In the two proposed network coding schemes, a node may perform a bit-wise exclusive or (XOR) operation to combine the native packet of itself and the native packet of its neighbour, called the coding neighbour, into an XOR coded packet. The reliability of all-to-all broadcast under both the proposed network coding schemes is investigated analytically using Markov chains. It is shown that the reliability of all-to-all broadcast can be improved considerably by employing the proposed network coding schemes, compared with non-coded networks with the same link conditions, i.e. same probabilities of successful packet transmission via wireless channels. Further, the proposed schemes take the link conditions of each node into account to maximise the reliability of a given network. To be more precise, the first scheme proposes the optimal coding neighbour selection method while the second scheme introduces a tuning parameter to control the probability that a node performs network coding at each transmission. The observation that channel condition can have a significant impact on the performance of network coding schemes is expected to be applicable to other network coding schemes for lossy wireless networks
Timely and reliable packets delivery over Internet of Vehicles (IoVs) for road accidents prevention: a cross-layer approach
With the envisioned era of Internet of Things (IoTs), all aspects of Intelligent Transportation Systems (ITS) will be connected to improve transport safety, relieve traffic congestion, reduce air pollution, enhance the comfort of transportation and significantly reduce road accidents. In IoVs, regular exchange of current position, direction, velocity, etc., enables mobile vehicles to predict an upcoming accident and alert the human drivers in time or proactively take precautionary actions to avoid the accident. The actualization of this concept requires the use of channel access protocols that can guarantee reliable and timely broadcast of safety messages. This paper investigates the application of network coding concept to increase content of every transmission and achieve improved broadcast reliability with less number of retransmission. In particular, we proposed Code Aided Retransmission-based Error Recovery (CARER) scheme, introduced an RTB/CTB handshake to overcome hidden node problem and reduce packets collision rate. In order to avoid broadcast storm problem associated with the use of RTB/CTB packet in a broadcast transmission, we developed a rebroadcasting metric used to successfully select a vehicle to rebroadcast the encoded message. The performance of CARER protocol is clearly shown with detailed theoretical analysis and further validated with simulation experiments
Completion Delay of Random Linear Network Coding in Full-Duplex Relay Networks
As the next-generation wireless networks thrive, full-duplex and relaying
techniques are combined to improve the network performance. Random linear
network coding (RLNC) is another popular technique to enhance the efficiency
and reliability in wireless communications. In this paper, in order to explore
the potential of RLNC in full-duplex relay networks, we investigate two
fundamental perfect RLNC schemes and theoretically analyze their completion
delay performance. The first scheme is a straightforward application of
conventional perfect RLNC studied in wireless broadcast, so it involves no
additional process at the relay. Its performance serves as an upper bound among
all perfect RLNC schemes. The other scheme allows sufficiently large buffer and
unconstrained linear coding at the relay. It attains the optimal performance
and serves as a lower bound among all RLNC schemes. For both schemes,
closed-form formulae to characterize the expected completion delay at a single
receiver as well as for the whole system are derived. Numerical results are
also demonstrated to justify the theoretical characterizations, and compare the
two new schemes with the existing one
Strong secrecy on a class of degraded broadcast channels using polar codes
Two polar coding schemes are proposed for the degraded
broadcast channel under different reliability and secrecy
requirements. In these settings, the transmitter wishes to send
multiple messages to a set of legitimate receivers keeping them
masked from a set of eavesdroppers, and individual channels are
assumed to gradually degrade in such a way that each legitimate
receiver has a better channel than any eavesdropper. The layered
decoding structure requires receivers with better channel quality
to reliably decode more messages, while the layered secrecy
structure requires eavesdroppers with worse channel quality to
be kept ignorant of more messages.Postprint (author's final draft
Practical LDPC coded modulation schemes for the fading broadcast channel with confidential messages
The broadcast channel with confidential messages is a well studied scenario
from the theoretical standpoint, but there is still lack of practical schemes
able to achieve some fixed level of reliability and security over such a
channel. In this paper, we consider a quasi-static fading channel in which both
public and private messages must be sent from the transmitter to the receivers,
and we aim at designing suitable coding and modulation schemes to achieve such
a target. For this purpose, we adopt the error rate as a metric, by considering
that reliability (security) is achieved when a sufficiently low (high) error
rate is experienced at the receiving side. We show that some conditions exist
on the system feasibility, and that some outage probability must be tolerated
to cope with the fading nature of the channel. The proposed solution exploits
low-density parity-check codes with unequal error protection, which are able to
guarantee two different levels of protection against noise for the public and
the private information, in conjunction with different modulation schemes for
the public and the private message bits.Comment: 6 pages, 4 figures, to be presented at IEEE ICC'14 - Workshop on
Wireless Physical Layer Securit
Resource Allocation Frameworks for Network-coded Layered Multimedia Multicast Services
The explosive growth of content-on-the-move, such as video streaming to
mobile devices, has propelled research on multimedia broadcast and multicast
schemes. Multi-rate transmission strategies have been proposed as a means of
delivering layered services to users experiencing different downlink channel
conditions. In this paper, we consider Point-to-Multipoint layered service
delivery across a generic cellular system and improve it by applying different
random linear network coding approaches. We derive packet error probability
expressions and use them as performance metrics in the formulation of resource
allocation frameworks. The aim of these frameworks is both the optimization of
the transmission scheme and the minimization of the number of broadcast packets
on each downlink channel, while offering service guarantees to a predetermined
fraction of users. As a case of study, our proposed frameworks are then adapted
to the LTE-A standard and the eMBMS technology. We focus on the delivery of a
video service based on the H.264/SVC standard and demonstrate the advantages of
layered network coding over multi-rate transmission. Furthermore, we establish
that the choice of both the network coding technique and resource allocation
method play a critical role on the network footprint, and the quality of each
received video layer.Comment: IEEE Journal on Selected Areas in Communications - Special Issue on
Fundamental Approaches to Network Coding in Wireless Communication Systems.
To appea
Speeding Multicast by Acknowledgment Reduction Technique (SMART)
We present a novel feedback protocol for wireless broadcast networks that
utilize linear network coding. We consider transmission of packets from one
source to many receivers over a single-hop broadcast erasure channel. Our
method utilizes a predictive model to request feedback only when the
probability that all receivers have completed decoding is significant. In
addition, our proposed NACK-based feedback mechanism enables all receivers to
request, within a single time slot, the number of retransmissions needed for
successful decoding. We present simulation results as well as analytical
results that show the favorable scalability of our technique as the number of
receivers, file size, and packet erasure probability increase. We also show the
robustness of this scheme to uncertainty in the predictive model, including
uncertainty in the number of receiving nodes and the packet erasure
probability, as well as to losses of the feedback itself. Our scheme, SMART, is
shown to perform nearly as well as an omniscient transmitter that requires no
feedback. Furthermore, SMART, is shown to outperform current state of the art
methods at any given erasure probability, file size, and numbers of receivers
An Efficient Network Coding based Retransmission Algorithm for Wireless Multicasts
Retransmission based on packet acknowledgement (ACK/NAK) is a fundamental
error control technique employed in IEEE 802.11-2007 unicast network. However
the 802.11-2007 standard falls short of proposing a reliable MAC-level recovery
protocol for multicast frames. In this paper we propose a latency and bandwidth
efficient coding algorithm based on the principles of network coding for
retransmitting lost packets in a singlehop wireless multicast network and
demonstrate its effectiveness over previously proposed network coding based
retransmission algorithms.Comment: 5 pages, 5 figure
- …